Conductive resin composition, process for production thereof, and fuel cell separators

Abstract

An object of the present invention is to provide a conductive resin composition which does not cause problems with regard to moldability such as occurrence of separation between a resin component and a conductive filler, voids and warp on molding, and is excellent in filling of a resin into a mold, and is also capable of being used for various electrical and electronic materials, including a separator for a fuel cell having excellent properties. To achieve the above object, the present invention provides a conductive resin composition comprising a conductive filler (A); a urethane-modified epoxy (meth)acrylate (B) obtained by reacting an epoxy (meth)acrylate (b-1), which is obtained by the addition reaction of an epoxy resin having an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit and a (meth)acrylic acid, with a polyisocyanate (b-2); a (meth)acrylate (C) having a number average molecular weight of 500 to 10,000, which contains 20 to 80% by weight of an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit and contains no active hydrogen atom; and the other ethylenically unsaturated monomer (D) which is copolymerizable with the urethane-modified epoxy (meth)acrylate (B) and the (meth)acrylate (C).

1. A conductive resin composition comprising:
 a conductive filler (A);
 a urethane-modified epoxy (meth)acrylate (B) obtained by reacting an epoxy (meth)acrylate (b-1) with a polyisocyanate (b-2); the epoxy (meth)acrylate (b-1) being obtained by an addition reaction of an epoxy resin having an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit and a (meth)acrylic acid; the epoxy (meth)acrylate (b-1) having a hydroxyl value in the range of 100 to 300; the molar ratio of moles of hydroxyl group of the epoxy (meth)acrylate (b-1) to moles of isocyanate group of the polyisocyanate (b-2) being within the range of 1.0/(0.5 to 1.5); 
 a (meth)acrylate (C) having a number average molecular weight of 500 to 10,000, which contains 20 to 80% by weight of an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit, and contains no active hydrogen atom; the (meth)acrylate (C) is a reaction product obtained by reacting a polyetherpolyol having an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit with a (meth)acrylic acid; and 
 the other ethylenically unsaturated monomer (D) which is copolymerizable with the urethane-modified epoxy (meth)acrylate (B) and the (meth)acrylate (C) 
 wherein a weight ratio of the urethane-modified epoxy (meth)acrylate (B) to the (meth)acrylate (C) is from 95/5 to 50/50. 
 
 
     
     
       2. A conductive resin composition according to  claim 1 , wherein the epoxy resin contains 30 to 90% by weight of an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit. 
     
     
       3. A conductive resin composition according to  claim 1 , wherein the epoxy resin is a novolac type epoxy resin. 
     
     
       4. A conductive resin composition according to  claim 1 , wherein the polyetherpolyol having an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit is an alkylene oxide adduct of a multinucleate phenolic compound. 
     
     
       5. A conductive resin composition according to  claim 1 , wherein the content of the conductive filler (A) is from 50 to 90% by weight. 
     
     
       6. A conductive resin composition according to  claim 1 , wherein the content of the conductive filler (A) is from 50 to 90% by weight, the content of the urethane-modified epoxy (meth)acrylate (B) is from 6 to 18% by weight, the content of the (meth)acrylate (C) is from 2 to 8% by weight, the content of the other ethylenically unsaturated monomer (D) is from 2 to 25% by weight, and the total percentage of (A), (B), (C), and (D) is 100%. 
     
     
       7. A conductive resin composition according to  claim 1 , wherein the ethylenically unsaturated monomer (D) is an aromatic vinyl monomer. 
     
     
       8. A method for producing a conductive resin composition, which comprises:
 (1) the first step of kneading a conductive filler (A), an epoxy (meth)acrylate (b-1) obtained by the addition reaction of an epoxy resin having an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit and a (meth)acrylic acid, a polyisocyanate (b-2), a (meth)acrylate (C), a reaction product obtained by reacting a polyetherpolyol having an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit with a (meth)acrylic acid, having a number average molecular weight of 500 to 10,000, which contains 20 to 80% by weight of an aromatic cyclic structural unit and/or an aliphatic cyclic structural unit and contains no active hydrogen atom, and an ethylenically unsaturated monomer (D); and 
 (2) the second step of reacting the kneaded mixture obtained in the first step with the (meth)acrylate (b-1) and the polyisocyanate (b-2) at a temperature of room temperature to 80° C., thereby causing chain elongation; 
 wherein the epoxy (meth)acrylate (b-1) has a hydroxyl value in the range of 100 to 300; and, the molar ratio of moles of hydroxyl group of the epoxy(meth)acrylate (b-1) to moles of isocyanate group of the polyisocyanate (b-2) is within the range of 1.0/(0.5 to 1.5). 
 
     
     
       9. A separator for a fuel cell obtained by molding the conductive resin composition according to  claim 1 . 
     
     
       10. A separator for a fuel cell obtained by molding the conductive resin composition according to  claim 2 . 
     
     
       11. A separator for a fuel cell obtained by molding the conductive resin composition according to  claim 3 . 
     
     
       12. A separator for a fuel cell obtained by molding the conductive resin composition according to  claim 5 . 
     
     
       13. A separator for a fuel cell obtained by molding the conductive resin composition according to  claim 4 . 
     
     
       14. A separator for a fuel cell obtained by molding the conductive resin composition according to  claim 7 . 
     
     
       15. A separator for a fuel cell obtained by molding the conductive resin composition according to  claim 6 .